Central java

The central part of java is much narrower than West- and East Java, measuring only 100-120 km across. This is because the Java Sea extend inland with a broad bight between Cheribon and Semarang, so that the northern lowland is more restricted or even absent, and because the Southern Mountains disappear for the greater part below sealevel between Nusa Kembangan and the Southern Mountains of East Java.

The northern coastal plain of Central Java has its maximum width (40 km) South of brebes, where the Pemali Valley separates the Bogor Range of West Java from the northern mountains of Central

Java. Farther East it Narrows to about 20 km South of Tegal and Pekalongan, until it disappears completely East of Pekalongan where the headland of the mountains reaches the coast. Between Weliri and Kaliwungu another fertile alluvial stretch is formed by the delta of the Bodri River.

The mountainland of Central Java is formed by two ge-anticlinal culminations, the North- and the South- Serayu Range.

The North- Serayu Range forms the connecting link between the Bogor Range in West Java and the Kendeng ridge in East Java. The South-Serayu Range is a new element rising from the longitudinal Bandung depression of West Java.

The North-Serayu-Range has a width of 30-50 km. its western end is capped by the Slamet Volcano (3428 m ), and its eastern part is covered by the young volcanic products of the Rogodjembangan Mts (2177 m), the Dieng complex (Prahu, 2565m), and the Ungaran (2050m). the borderline with the Bogor Range of West Java runs across Prupuk- Bumiayu-Adjibarang.

Between the North- and the South Serayu Range there is again a longitudinal depression, the Serayu Zone, in which are situated the places Majenang, Ajibarang, Purwokerto, Banjarnegara, Wonosobo.

Between purwokerto and Banjarnegara the Serayu Zone has a width of 15 km; East of Wonosobo it becomes broader, but here the depression is partly filled and masked by the young volcanic cones if the Sundoro (3155m) and Sumbing (3371 m ). Orographically it appears again in te plain of Temanggung- Magelang, which is the first of a series of intermontane plains in East Java.

The South-Serayu Mts consist of a western and an eastern part. The western one (with Kabanaran 360m) might be described as an elevation in the Bandung-depression Zone of West Java, or as a new structural element belonging to Central Java. It is separated from the Bogor Range by the Majenang palinn and upper course of the Tjihaur and Pasir.

The eastern part of the South-Serayu Range forms a ge-anticlinal elevation in this depression zone of Bandung, comparable with the culmination of the Bayah Mts at its wetern end. The eastern part of the South-Serayu Range is completely separated from the western one by the Jatilawang Valley. It starts near Ajabarang as a simple, narrow anticline, transversely cut by the Serayu River. East of Banyumas this anticline develops into an anticlinorium of some 30 km width in the Lukulo (Loh Ulo) area, South of Banjarnegara (Midangan 1043 m). the eastern end of the South-Serayu Range is formed by the more or less independent dome of the West-Progo Mts (1022m), between Purworejo nad the Progeo River.

The Coastal Plain of South Central Java is 10-25 km wide. This part of the South coast forms a sharp contrast with the rocky South coast of West and East Java, lying not more than 10 m above sealevel. Three shore bars with dunes of 5-15 m height and 100-500 m width run parallel to the coast, the youngest one still being subjected to changes. This low coastal stretch joins on to the Bandung Zone of West Java. It is interrupted in the middle part by the Karangbolong Mts (475m), which are the physiographical and structural equivalent of the Southern Mts in West and East Java. Apart from this

relic, these Southern Mts have subsided below sealevel between Nusa Kambangan and the mouth of the Opak river.